1. Field of the Invention
The present invention relates to a rechargeable battery and a battery module, and more particularly, to a rechargeable battery having an improved structure for electrically connecting electrode terminals and rechargeable batteries, and a battery module.
2. Description of the Related Art
Unlike a primary battery that cannot be recharged, a rechargeable battery (i.e., secondary battery or a secondary cell) can be repeatedly charged and discharged. A low capacity rechargeable battery is used for small electronic devices such as mobile phones, notebook computers, camcorders, and the like, and a large-capacity rechargeable battery is commonly used as a power source for driving a motor of a hybrid electric vehicle and the like.
Recently, a high output rechargeable battery using a non-aqueous electrolyte with high energy density has been developed, and it is formed as a large-capacity rechargeable battery configured by connecting a plurality of rechargeable batteries in series so as to be used for driving a motor of a device, i.e., an electric vehicle, and the like, that requires high power. In addition, a single large-capacity rechargeable battery generally includes a plurality of rechargeable batteries connected in series. The rechargeable battery may have a cylindrical or angular shape.
The angular rechargeable battery includes an electrode group (i.e., an electrode assembly) including a positive electrode and a negative electrode positioned with a separator interposed therebetween, a case with a space for housing the electrode group, and a cap plate for sealing the case and having a terminal hole into which an electrode terminal is inserted, the electrode terminal being electrically connected with the electrode group and inserted into the terminal hole so as to outwardly protrude from the case.
The rechargeable batteries are electrically connected by a connection plate to constitute a battery module. The electrode terminal is fixed to the cap plate by a nut combined at an upper portion of the electrode terminal, the connection plate is fastened on the nut, and a nut is fastened to the connection plate, whereby the connection plate and the electrode terminal are electrically connected. The fastening force of the nut needs to be strengthened to reduce contact resistance between the electrode terminal and the connection plate. In particular, the fastened nut may become loose due to vibration transferred to the rechargeable battery, and in this case, in order to prevent an increase in the contact resistance, the nut should be tightened strongly.
The electrode terminal serves as a passage of current, so it is preferably made of a material of good electrical conductivity. In general, the positive electrode terminal is made of aluminum, while the negative electrode terminal is made of copper.
Copper and aluminum are weak so there is a limitation in increasing the fastening force of the nut. Thus, when vibration, temperature change, an impact, or the like occurs, in many cases the nut loosens and the contact resistance increases.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.